1. Field of the Invention
The invention generally relates to a mix formulation for the production of biodegradable goods and methods for use of said formulations.
2. Background
Conventional disposable food service items are commonly made from paper or paperboard (commonly coated or impregnated with a polymeric water-proofing material such as wax or polyethylene), or one of a variety of plastics (polystyrene is the most common). These materials have good to excellent resistance to moisture, can be made insulating (foamed polystyrene or “Styrofoam”), and are inexpensive and durable. The industrial production methods used to produce disposable packaging from these materials are mature; these items can be produced quickly and relatively cheaply in great quantities.
There is, however, a growing recognition that the environmental costs of using these “cheap” materials may be quite high. The expected lifetime of a polystyrene cup, for example, is about 500 years, and each American disposes an average of about 100 cups per year. Further, polystyrene is made by chemical processing of benzene and ethylene, both byproducts of the petroleum industry, and thus both non-renewable resources. Although the environmental record of the petroleum industry has improved greatly since the mid-twentieth century, extraction and processing of petroleum for fuel and chemical production remain recognized environmental problems.
Paper and paperboard are made from wood pulp, which is a renewable material. The regeneration time, however, for wood fiber—the time required to grow a tree—is substantial, and the chemical processing needed to produce white fibers has been recognized to be detrimental to the environment. The use of unbleached and recycled fibers helps alleviate these environmentally detrimental activities, but the use of slow-growing trees as a fiber source when many agricultural byproduct sources are available is in itself questionable.
The pressure to use biodegradable disposable packaging materials has been steadily increasing in the last decade. As recently as March, 2003, Taiwan outlawed the use of polystyrene foam in disposable packaging. China's major cities (e.g., Beijing and Shanghai) have also outlawed the use of polystyrene foam in disposable packaging.
To address the environmental concerns about conventional disposable food container products, one approach in the art has been the manufacture of starch-based disposable food service items such as trays, plates, and bowls. Starch-based packaging used in the art, however, currently has several drawbacks, the most important being that the containers are susceptible to water.
Specifically, cooked, unmodified starch is inherently water soluble. Because all of the starch-based biodegradable food service items currently being manufactured are formed in heated molds, much or all of the starch in these items is cooked, and the products thus formed are very sensitive to moisture. When exposed to water, other aqueous fluids, or significant amounts of water vapor, these items become very soft, losing form-stability and becoming susceptible to puncture by cutlery (e.g., knives and forks).
Manufacturers currently address the problem of the moisture-susceptibility of starch-based food-service items in two ways, either by not using the products in aqueous environments or by applying a coating to the product. One approach is to avoid the problem simply by marketing their food service items for uses in which aqueous fluids or vapor are not present (e.g., dry or deep-fried items). This approach greatly limits the potential markets for these items, since many food products either (1) are aqueous (e.g., beverages, soups), (2) include an aqueous phase (e.g., thin sauces, vegetables heated in water) or (3) give off water vapor as they cool (e.g., rice and other starchy foods, hot sandwiches, etc.)
Another approach is to protect the starch from contact with aqueous fluids or vapors by applying water-resistant coatings or films to the surfaces of the food service items, essentially forming a laminated structure in which a water-sensitive core is sandwiched between layers of a biodegradable water-resistant material. Many biodegradable coatings, however, are costly to obtain and difficult to apply, thus increasing manufacturing cost and complexity and reducing the percentage of acceptable finished products.
Further, in the current art, the mechanical properties of the matrix material (mainly starch) are critical to the performance of starch-based food service articles. Baked unmodified starch is typically quite fragile and brittle when dry, but relatively soft and pliable when the starch contains 5% to 10% moisture. In current practice, fiber is often added to the formulation to increase the flexural strength and fracture energy of starch-based items, especially during the period immediately after demolding, when the moisture content of the starch is very low. Even with the addition of significant amounts (10% or more) of fiber, however, starch-based articles are commonly very brittle immediately after demolding or when stored for extended periods in dry environments (heated buildings in winter, air conditioned buildings in summer, desert environments any time of year). Brittle failure of starch-based articles thus continues to present problems during the manufacturing process (especially before coatings or laminated films are applied) and when the articles are used in dry environments.
Moreover, in the current art, inorganic mineral fillers (e.g., calcium carbonate, silica, calcium sulfate, calcium sulfate hydrate, magnesium silicate, micaceous minerals, clay minerals, titanium dioxide, etc.) are often included in formulations used to produce starch-based biodegradable food service articles. These fillers are not, however, biodegradable. Marketing claims made for products using these materials as fillers point out that the materials are natural, renewable, and environmentally benign. However, there are inherent environmental costs associated with the mining (or synthesis) and processing of all inorganic filler materials.
Finally, in the current art, the most commonly used fiber in starch-based food service articles is wood-pulp fiber (similar to the paper based articles). As the main source material for the paper industry, it is readily available, is consistent in quality and material properties, and has the main properties needed to serve as structural elements in the finished food service articles. The use, however, of slow-growing trees as a fiber source when many agricultural byproduct sources are available is, as set forth above, in itself questionable.
Accordingly, there is a need for an improved system for producing water-resistant, biodegradable disposable items that can serve the full range of uses to which containers, boxes, plates, trays, and bowls are usually put, but which avoids the cost and complexity of film lamination or spray coating systems.
There is also a need for a means to enhance the mechanical properties of the matrix material in starch-based food service articles, in order (a) to ease handling requirements during manufacture and (b) to enhance usability in dry environments.
There is also a need for an improvement in the current art that will replace mineral fillers with fully biodegradable and renewable plant-based organic materials that serve the same role as traditional mineral fillers. Even greater benefit is available if the filler material is currently produced as a byproduct of the production of another agricultural material.
There is also a need for methods and formulations that incorporate fibrous materials from non-wood plants, and particularly from materials that are by products of commodities already in production.